1. Field of the Invention
The present invention relates to a control apparatus incorporated in a cigarette production machine and used to control the diameter of cigarettes or a tobacco rod during the formation thereof.
2. Description of the Related Art
In a process for running an elongate paper in one direction, a cigarette production machine first forms a tobacco rod while continuously wrapping shredded tobacco in the paper, and then cuts the formed tobacco rod into individual cigarettes with a predetermined length.
More specifically, the tobacco rod is formed in the following manner. On receiving the shredded tobacco, the paper travels on a lower mold. During this traveling process, the paper is first curved by means of the lower mold into a U-shaped configuration such that it envelops the shredded tobacco from below. As the U-shaped paper passes between the lower mold and a first upper mold, thereafter, one side of the paper is curved by means of the first upper mold into an arcuate configuration such that it overhangs the shredded tobacco. As the U-shaped paper then passes between the lower mold and a second upper mold, moreover, the other side of the paper is also curved by means of the second upper mold into an arcuate configuration such that it overhangs the shredded tobacco in like manner. At the same time, the other side of the paper is lapped and pasted on the one side, whereupon the tobacco rod is completed.
Since the tobacco rod is continuously formed by means of the lower and upper molds while the paper is traveling, as described above, it is very difficult to stabilize the diameter of the formed tobacco rod. Inevitably, therefore, the diameter of the tobacco rod varies in some measure during production.
If the diameter of the tobacco rod is greater than allowable limits, however, the width of a lap portion at which the opposite side edges of the paper meet is so narrow that the two edges cannot be perfectly pasted together, and the shredded tobacco cannot be wrapped in the paper in some cases.
After the cigarettes are produced in this manner, filter cigarettes may be obtained by connecting a filter plug to each cigarette by means of a tip paper piece. If the diameter of the cigarettes or tobacco rod is subject to a substantial variation, in this case, the connection of each cigarette and the filter plug by means of the tip paper piece is imperfect.
Thus, if the diameter of the tobacco rod is too small, a gap is inevitably formed between the tip paper piece and each cigarette due to the difference in diameter between the filter plug and the cigarette. Since this gap causes an undesirable increase of the amount of air which flows through the filter plug into a smoker's mouth, constituents of tobacco smoke change, thereby exerting a bad influence upon the taste of the tobacco.
If the diameter of the tobacco rod is too large, on the other hand, the compressive force of the paper on the shredded tobacco is so small that the tobacco may slip out of the cut end of the cigarette, or that the cigarette itself is liable to be deformed or spoiled in external appearance.
If the difference in diameter between the filter plug and the cigarette is great, moreover, the tip paper piece is liable to winding failure, so that it creases. Thus, the external appearance of the filter cigarette is considerably damaged.
In consideration of these circumstances, an operator of the cigarette production machine monitors time lap width of the tobacco rod during the operation of the machine. If the lap width is deviated from an allowable range, the operator must manually operate the second upper mold to adjust its position with respect to the lower mold. The diameter of the tobacco rod can be set within the allowable range by this adjustment.
Visual inspection of the lap width of the tobacco rod is very difficult, however, since the tobacco rod itself is traveling at high speed with deflection. Since the position of the second upper mold is manually adjusted, moreover, the accuracy of the position adjustment depends substantially on the operator's skill.
Accordingly, there is a demand for the development of an apparatus which can automatically adjust the diameter of the tobacco rod, and this development first requires an accurate measurement of the rod diameter. As mentioned before, however, the tobacco rod undergoes deflection as it travels, so that measuring its diameter is a very hard task.